Hydraulic clutch



June '12, 1923. 1,458,565

W. WESTON HYDRAULIC CLUTCH Filed May '7, 1920 5 Sheets-Sheet 2 /7 l a311 7a G f E 8 /9 .17 k P u June 12, 1923. 1,458,565 I W. S. WESTONHYDRAULI C CLUTCH Filed May 1920 S-Sheets-Sheec 4 3V FPS A C W 6666" vInventor:- MW ,J m

June 12, 1923 1,458,565 w. s. WESTON HYDRAULIC CLUTCH' Filed May '7,1920 5 Sheets-Sheet 5 Patented June 12, 1923.

-lTED SATES WILLIAM s. was-roar, or DALLAS, 'rnxas.

HYDRAULIC CLUTCH.

Application filed may 7, 1920. Serial No. 379,654,

To all whom it may concern:

Be it known that I, WILLIAMS. Wnsrorr, a citizen of the United States,residing 1n the city of Dallas, county of Dallas, andv State of Texas,have invented certain new and useful 'Improvements in a HydraulicClutch, of which the following is a full, clear, and exact description.

My invention relates to improvements in that class of clutches in whichthe opening and closing operation is obtained by a manipulation of thevalves governing the flow of a li uid medium through the elements of ahy raulic pump, and in which the pump casing, with the elements normallystationary considered as a pump, constitute one member of the clutch,and the pump operating shaft with its attached parts constitute theother member. Many types of such a clutch have been devised. The primaryimprovements of my present invention apply preferably to that type inwhich the pump elements acting directly on the liquid medium are a pairof intermeshing spur gears.

The object of my invention 15 the attainment in a clutch of thischaracter of a high rate of efiiciency in both the open and closedposition together with greater simplicity 1n construction and a moreperfect control in operation.

All the essential parts in the construction of a hydraulic clutch of theclass describedl embodyin the new and improved features whereby f attainmy object, together with other novel features of auxiliary value arehereinafter fully described and clearly illustrated in the accompanyingdrawings, which form a part of these specifications. The elements ofnovelty are particularly pointed out in the claims.

Fig. 1 is a side elevation of the clutch illustrating how it may beattached to the motor fly wheel and used in the place of the cone orfriction disc clutch of an automobile or motor driven vehicle. Thefly-wheel and means of attachment thereto not being an essential elementin this invention, are shown in dotted out-line in this figure only.Fig. 2 is'an end elevation, as seen from the right of Fi 1. Fig. 3 is anend elevation of the malnclutch casing as seen from the left of Fig. l,withthe cover plate on the end removed. Fig. l is a similar view, asseen from the right of Fig. 1, with the cover plate on that end removed.In Figs. 3 and a the bolts and parts that pass through the cover platesare shown in section. Fig. 5 s a vertical longitudinal section of Fig.l, drawn to a larger scale as viewed on the line 5-5 of Figs. 2, 3, and4, in the direction indicated'by' the arrows. I ig. 6 is a trans versesection of the mainclutch casing on the line 66 of Figs. 5 and 9. Fig. 7is the same as Fig. 5 with the controlling valves shifted to the openposition. Fig. 8 is a transverse section of the main clutch casing ontheline 8-8 of Fig. .7, and on;

the same line of Fig. 9, assuming the controllin valve shown in thatfigure to be shifte to open osition. Fig. 9'is a longitudinal sectionthrough one side of the main casing and cover plates on the line 9-9 ofFigs. a and 6, showing'one controlling valve in the closed position. TheFig. 9 section is also indicated b the line 9-9 of Fig. 8, which, asstated a ove, is a transverse section with the controlling valves open.Fi 10 is a side elevationsimilar to Fig. 1 wit the left hand half of themain casing shown in vertical longitudinal section, illustrating how theclutch may be utilized to connect a pulley-with a drivingline shaft.Figs. 11, 12,13 and 14 are mathematical diagrams used to illustrate theintermeshing relation of spur gears havin% teeth with cylindricalcontact surfaces. igs. 15 and 16 are enlarged views of the gear recesstaken from the samapoint of view as Fig. 3 and used to illustrate moreclearly a detail essential to the practical operation of the clutch whenconstructed with that type of" gear. The same letters and numerals ofreference marked on the drawings refer to the same parts in the severalviews.

My improved hydraulic clutch, first described in general terms,comprises'in its two fundamental elements a. rotating casingconstituting the driving member and a shaft or its equivalent,concentric with the casing and constituting the driven member.

Within the driving casing immediately.

under the left hand cover plate, as illustrated, is a close fittingfigure 8 recess containing a pair of intermeshing spur gear pump gears.One of these gears,called the primary gear, is concentric with thecasing and is attached to or made integral with the driven shaft; Theother gear, calledv the secondary gear, is journaled in the casing,preferab y on one of the construction bolts, and is free to be rotatedin a planetary movement about the primary gear when such rotationis notprevented by a liquid medium which may be confined in the interdentalspaces of the gears and within the gear recess. In operation a freeplanetary movement is the condition'for the open clutch while aninter-lock of the gears with the liquid medium is the condition for theclosed clutch.

W'ithin the casing immediately beneath the right hand cover plate, asillustrated. is a relatively large storage chamber containing a liquidmedium, preferably a moderately viscous lubricating oil.

Within the cast body of the casing and leading between the figure 8 gearrecess on one end and the storage chamber on the other are a series ofpassages and valves providing for and governing the .flow of the liquidmedium to and from the gear recess. The passages are so arranged and thevalves may be so controlled that one or the other of the two operatingconditions above referred to maybe obtained. First. for the operatingclosed position of the clutch the gear recess is maintained full of theliquid medium and the passages are so connected together and closedagainst a return of the liquid to the storage chamber,

that the gears will be interlocked for all normal loads for which theclutch is designed, or second, for the operating open position of theclutch the passages are so connected and opened that the gear recess ismaintained empty of any appreciable amount of the liquid medium, therebypermitting a free planetary movement of the secondary gear about theprimary. Thearrangement of the passages and the controlling valves forthis second or operating open position of the clutch is an importantnovel feature of my invention.

In it I take advantage of the centrifugal.

action on the liquid medium in the rotating casing to assist in clearingthe gear recess and interdental spaces of all liquid. By thisconstruction I am able to use a slow running viscous liquid with a lowleakage ratio for the operating closed position, and

cloidal surfaces, as in the standard machine gear. This type of gearenables me to obtain and maintain'more readily a liquid tight jointbetween the gears at the l nes of the clutch.

of intermesh and between the gears and the peripheral walls of therecess, so that in The driving casing A is a single casting in which therecesses, passages, valve seats and storage chamber, partly formed bycoring, may befinished in a lathe or boring mill. The left end is fittedwith a cover plate B and the right end with a cover plate C. The casingand cover plates are held together with fluid tight joints by means ofbolts D. The cover C is provided with a hub E. Extending through the huband concentricboth with the hub and casing is the driven shaft F. Thehub is fitted with an interior lining of anti-friction metal 0surrounding the shaft to provide for wear when the casing is rotatingand the shaft is stationary in the operating open position On theexterior of the hub is a sleeve G, adapted to have a longitudinalmovement on the hub and thereby be utilized to change the clutch throughvalve mechanism yet to be described from the opened to the closedposition, or vice versa. The movement of the sleeve may be obtained bymeans of a shifter fork, fitted to the groove g. The shifter fork is awell known mechanism and need not be illustrated or described.

In the driving casing immediately under the cover plate B is the figure8 recess H, containing in a liquid tight fit on peripheral and facesurfaces the primary gear P and the secondary gear S. The fit is suchthat when the interdental spaces and any small chambers connected toopposite sides of the recess are filled with a liquid and the outletsfrom these opposite sides are closed, any intermeshing movement of onegear on the other will develop compression on one side of the recess andsuction on the other. The primary gear P is mounted on and preferablymade integral with the shaft F.

The shaft is extended beyond the gear so as to have a short bearing in asocket in the cover plate B, which is preferably lined with antifrictionmetal 6. The secondary gear S is mounted to rotate freely on one of thestructure bolts D.

In the driving casing under the cover plate C is a chamber J for holdingin storage a quantit of liquid suflicient for operation in bot theoperating opened and closed positions. The central portion of thischamber around the shaft F is, separated from the radially outer portionby a cylindrical ring formation K of the main casing casting which doesnot uite reach the cover plate C. The two portions of the chamber aretherefore connected by a narrow annular opening around the edge of thering. The interior surface of the ring is conical and increases indiameter toward the edge. The construction is such that when the casingis rotating, any liquid in the central portion of chamber J will flow bycentrifugal action toward and around the edge of ring K into the outerportion.

'The central portion of the chamber is divided into two compartments byoppositely positioned partitions L L, extending from the inner surfaceof the ring toward the shaft F and coming sufiiciently close to theshaft to form a practically liquid tight joint without taking a bearingon the shaft. The purpose of these partitions will be stated later on;

Before going into the description of the several passages and valves, itshould be stated that the preferred form of my invention, asillustrated, is operable with the driving casing rotating in eitherdirection. In this construction the passages and valves are made induplicate and symmetrically opposite sets. To avoid confusion in thefollowing description, the rotation: of the casing will be considered ascounter clockwise when viewed from the right-of Fig. 1 and as seen inFigs. 2, 4, 6 and 8, the direction being indicated by the arrow 1.Referring to Fig. 6, with rotation "counter clock-wise any liquid orfluid in the gear recess will be subject by the relative gear movementto compression on one side in the region marked by the numeral 2 and tosuetion in the opposite region marked by the is numeral 2 with a sufiixsmall a. Using this method of distinguishing the similar opposite parts,the passages and valves associated with the compression side of the gearrecess are referred to by numerals while those 'associated with thesuction side are referred to by the same numerals with the suflix smalla.

Referring to Figs. 5, 6 and 7, the parts 3 and 3 are piston valves,having stems 4 and 4* extending through the cover plate C and attachedto wings 5 and 5 on the shifter sleeve G. Fig. 5 show'sthese valves inthe closed positionof the clutch and Fig. 7 in the open position, aswill be understood after a little further consideration. Passages 6 and6* lead from the gear recess to the piston valves 3 and 3 respectively.Ducts 7 and 7 extending through the piston valves connect passages 6 and6 in the closed position of Figs. 5 and 6, with passages 8 and 8 thatlead into small chambers 9 and 9", which are provided with check valves10 and 10, that close openings into the stora e chamber J The check"alves are preferab held to their seats by light springs and are sodesigned ,as to open only to a suction action from the gear recess orfrom pressure of the liquid in the storage chamber under centrifu alaction.

.A stu y of Fig. 6 made now following the description given in thepreceding paragraph discloses the operation of the device in the closedposition. Any tendency of the secondary gear S to move counterclock-wise about the primary P draws in liquid from the storagechamberby suction action through the check valve 10 and maintainssuction regions or passages 2 6 7*, 8 and 9 full while the check valve10 prevents discharge from-the compression regions2, 6,

7, 8 and 9. It is clear, therefore, that for.

this position with a practically incompressible liquid the secondarygear cannot have a planetary movement about the primary and that theprimary with the shaft F must rotate with the casing. It should be notedthat the check valves'10, 10, the storage chamber ends ofwhich are shownin Fi s. 4 and 8, are located near the peripheryo the driving casingwhich is always rotating when in operation and will therefore always besub- Ibperged by the liquid in the storage chamer. sion leak back aroundthe piston valve 3 or check valve 10, or around theshaft F will bereplenished immediately and continuously through the check valve 10". Itis also well Any liquid that may under eompres- I to note in thisconnection that, with the suc-.

central portion of the chamber J. It can be' seen in Fig. 7 that theducts 7, 7 are entirely out of register with the passages 8, 8*, shownpartly in dotted outline, which lead to the check valves. The suction ofthe gears therefore cannot draw liquid through the check valves and canonly be replenished by .drawing liquid from the central portion ofchamber J by way of the passage 11. As already stated, this centralportion during operation is kept practically empty due to thecentrifugal action on the liquid. By this novel construction I am ablein the operating open clutch position of the piston valves to maintainthe gear recess and the adjoining passages practically free of theliquid medium, securinga free planetary movement of the iso which itwill be discharged by centrifugal force. It will now be apparent thatthe function of the radial walls or partitions L, L, dividing thecentral portion of chamber J into two halves, is to prevent the liquiddischarged from the compression side going back by centrifugal action aswell as suction action into the suction side.

The approximate maximum quantity of liquid that may be used in thedevice will be just enough to fill the-outer portion of the chamber Jwhen the gear recess, the connected passages on the compression andsuction sides, and the central portion of the chamber are substantiallyempty, as described in the preceding paragraph.

It is to be noted that normally the spaces empty of liquid will containair or gases from the liquid at atmospheric pressure. When the clutch isoperating in the open position, the planetary movement of the secondarygear about the rimary causes the device to act like a positive blower,driving a current of air or gas from the compression side through thetwo halves of the central chamber and back into the suction side.

This current is depended upon to blow out the excess of any liquid thatmay accumulate under centrifugal action in the vicinity of the duct Tinthe piston valve on the compression side, and to suck in any that mayaccumulate in the vicinity of duct 7 on the suction side. This aircurrent action is utilized in a provision hereinafter described forkeeping the gears lubricated when running in the open position for a.long period of time.

An understanding of the important action that takes place during theperiod of shifting the piston valves from the open to the closedposition, or vice versa, may be obtained from the study of Fig. 9 inconjunction with Fig. 7. Fig. 9 is a longitudinal section through thepiston valve 3 and the associated passages on the compression side ofthe gears, as indicated by the line 9-9 in Figs. 6 and 8. In this figurethe piston valve is in the closed position and a clear opening is shownfrom region 2 of the gear recess through passage 6, duct 7, passage 8small chamber 9, to the check valve 10. When the piston valve is pulledout for the open position, as shown in Fig. 7, it is moved 'just enoughto close the opening from passage-6 to passage 8 without making anopening from the passage G'into the space 12 under the piston. In thisposition from which the section of Fig. Sis taken, a clearopening willbe had from region 2 through passage 6, duct 7, and passage 11 to thecentral portion of chamber The especial feature now to be noticed isthat the duct .7, throu h the valve, is wider than the partition wa l 13between passage 8 and passage 11 and that for a period inthe movement ofthe valve from one to the other of its two operating positions thepassage 6 from the gear recess will be opened into both passages 8 and11. The same condition also develops simultaneously in the passages on.the suction side of the system. The result during this intermediatestage will be that both air and liquid will be drawn in on the suctionside and discharged into the central chamber from the compression side.As the movement for closing the clutch goes on through this stage, theinward fiow of li aid on the suction side will be facilitated w ile thedischarge from the compression side will be retarde The final operation,more or less gradual at the will of the operator, of 'closing off thecompression side from the central chamber. is a feature of paramountimportance, distinguishing the' hydraulic clutch from all other types.The manipulation of the piston valves through this middle positionconstitutes-the means, entirely free of uncertain or variable frictionstrains, whereby the full rotating movement of the driving casing may bevery gradually developed in the driven shaft in the process ofovercoming the inertia of the parts or the resistance of the load.

Provision is made to avoid the sudden closing of the clutch by aninexperienced operator. lVhen in the 0 en position the space 12 at thebottom of t e piston socket fills with liquid coming finally through thecheck valve and the passage 8, see. Fig. 7, or gradually down through alongitudinal groove 14 in the wall of the valve socket, leading into thestorage chamber. When the valve is started toward the closed position,the liquid in space 12 must all go out through the groove 14, as none ofit even in the beginning of the movement can go back into passage 8against the check valve. The retardation of movement, due to thenecessity of .forcing a comparatively large quantity of liquid throughthe small groove 14 is the well known dash pot effect and is wellunderstood. On the other hand, with the development of a momentaryvacuum in the dash pot space, the piston valves may be.

ner ends of relief valve and its duplicate 15 are shown .in crosssection in Fig. 8 projecting into passages 6 and 6 respectively. A veryheavy spring is used and its tension is so adjusted that it will allowthe valve to open only when the hydraulic pressure developed on thecompression side, by the transmission of the power load through theclutch, is increased by an excess load or otherwise to .a point whenstrains in the parts of the mechanism would be greater than those forwhich it was designed. This relief valve would be of especial value inthe application of my clutch to the driving of machinery subject tointermittent loading and sometimes dangerous overloading. My

I improved clutch may be used to advantage with constant speedmotorswith the relief valve so adjusted that the motor will continue runningat its normal speed, delivering its maximum power during moments ofoverloading. This use is especially applicable in driving machineshaving heavy fiy wheels designed to overcomesudden overloads, as withthe relief valve properly adjusted the full power of the motor is stillback of the fly wheel during the period the latter may be giving up someof its momentum.

In the application of my clutch to the driving of various kinds ofmachinery, conditions may frequently exist where the device will be runfor a long continuous period in the open position. For such a conditionprovision is made for insuring the lubrication of the gears by placingsmall leak holes 16 and 16*, leading from the storage chamher intopassages 11,.11 The liquid that leaks into passage 11 will be suckedthrough the gears and with the portion that leaks into passage 11 willeventually be blown back again into the storage chamber. The amount ofliquid provided by these leakholes will be relatively small and will notin any way interfere with the free planetary movement of th secondarygear. I

Lubrication of the bearing between the shaft F and the anti-frictionmetal lining of the hub E for "conditions of long operation in the openposition may be obtained by providing the usual journal oil groovesleading from the storage chamber.

The structural joints of the device, suchas those. between the maincasing and the cover plates and around the bolts, are made liquid andair tight by means of a paint or other joint cement. The structuralbolts D, where they pass through the storage cham ber, are greferablysurrounded b metal columns 1 which are cast with t e main casing andhelp to support the cover C.

Stufiing boxes 18, 18, are provided where the piston valve stems passthrough to the exterior, and a stuffing box 19 is provided for the jointbetween the end of the hub E and the driven shaft F. It should be notedthat My hydraulic clutch, as illustrated, and I thus far described, isuniversal in respect that it is operable when'the driving member isrotating in either direction and that for the closed position itconstitutes a positive union between the members. For instance, thisconstruction would revent the driven member from racing un er anyexterior impulse at a greater speed of rotation than that of the drivingcasing. As an example, in the casing of an automobile running down gradeunder the action of gravity, the clutch would still be in operationafter the gas supply to the engine had been cut off, with the automobiledriving the dead engine against the compression in its cylinders. litshould be noted, however, that for driving a shaft always in onedirection under conditions where provision against rac-v ing isunnecessary, a clutch embodying the fundamental feature of my device,whereby I maintain a gear recess liquid full for the.

liquid, while the compression side would be closed to the storagechamber, thereby maintaining the gear recess full of liquid and lockingthe gears against intermeshing movement. On the other hand in theoperating open position of the clutch, boththe suction and thecompression sides would have an opening into the central portion of thechamber which discharges by centrifugal action into the outer portionthereby resulting in the substantial clearance of all liquid from thegear recess and permitting the free intermeshing movement of the gears.For the one way construction an auxiliary relief valve, if used, wouldbe needed only on the compression side of the gears.

It is obvious that vmany changes in the form and adaptation of myinvention may be made without any modification of the fundamental novelfeatures on ,which its operation is based. Such a change is illustratedin Fig. 10. In this particular adap- In the operating closed iao tationthe driving'casing is keyed to a line shaft 21 and held in position by aset screw 22 in the end of the hub E, while the driven member carryingthe primary gear is made in the form of a sleeve 23, running on the lineshaft and extending through the left hand cover plate B. A pulley 24, orany other means for connecting u to the machinery to be driven when t eclutch is closed, may be keyed to the outer end of the sleeve. Thecoverplate B at the opening for the sleeve is provided with a hub 25 anda stufiing box ca 26 to prevent leakage to the exterior. Hy raulicpressure against this stuffing box is relieved by means of oil holes 27leading through the sleeve to the usual oil ooves that may be cut in itsinterior sur ace so as to lead back toward the central chamber. Astuffing box 28 is also provided for the outer end of the sleevecovering the exterior joint between the sleeve and the line. shaft 21. Abrake band 29 is adapted to hold the pulley stationary when the clutchis in the open position. Means are provided, such as the grease cup 30,for lubricating the interior of the sleeve when the line shaft isrunning with the clutch in open position and the sleeve, together withthe pulley, are held by the brake. The valve construction and all otherdetails pertaining to the manipulation and operation are in no waychanged.

As stated in the preliminary description of my invention, a primaryobject in the choice of the special gears having cylindrical surfaces ofcontact on opposite sides of the teeth as shown, instead of cycloidal orinvolute surfaces is to provide a construction that will give a minimumof leakage between the gears for a maximum of liquid to be displaced. Itis also my object to hold the driving casing to as small a diameter aspracticable for the power to be transmitted. These objects are bestobtained by the use of gears with a small number of large teeth.

The cylindrical contact surfaces may be defined as such that all pointsin these surfaces on both sides of any tooth are a constant radialdistance from a line arallel with the axis of the gear, constituting theaxis of the tooth and hereinafter called the center of the tooth. In theintermeshing movement the opposite cylindrical surfaces of a tooth havea rolling sliding contact with short parallel faces of the interdentalspace of the companion gear. As one tooth comes out of such doublecontact the incoming tooth of the companion gear comes into doublecontact.

I am aware that cylindrical teeth have been used before, but in only oneof a pair of gears, as in the squirrel cage pinionmembers of manyclocks. I am also aware that engineers and dra'ftsmen have illustratedintermeshing gears with more or less cylinof operation.

drically sha ed teeth on both gears, as for instance in t e patent to E.Nefi, et al., No.

275844, April 17-, 1883, for a rotary double piston pump. I am notaware, however, that intermeshing gears with teeth in each gear, each.provided'on op osite sides with true cylindrical surfaces a apted tohave a rolling sliding contact between short parallel facesin theinterdentalspace of the companion gear have ever been put into anypractical use, or have ever before been used in the construction of ,ahydraulic clutch. Neither am I aware that the intermeshing relation ofsiiich gears and their limitations have ever been fform'ulated and we;to. h shape as to enablethe mechanic mine the .correct practical:spacing" gear centers after havi size of the teeth and gear. v

In the beginning of this description it is to be noted that a air ofgears with cylindrical teeth cannot 0th have a relative uniform,rotative movement about their axes, a prime essential governing themanufacture of gears with cycloidal or involute contact surfaces. If onesuch gear with cylindrical teeth has a uniform rotation movement thecompanion gear will have a motion accelerated and retarded alternatelyat the passing of every tooth, setting up a rhythmic vibratory action.This feature makes the use of the cylindrical tooth in both gearspractically prohibitive in all construction where power is to betransmitted or work done by the""actual intermeshing movement of thegears, as in all machine gears and in spur gear pump gears operating aspum s. The rhythmic acceleration and retarda ion would necessarily betransmitted to the load, or forward or backward in the machinery, unlessabsorbed in some sort of cushion couplings.

The distinguishin characteristic in my use of gears with cy indricalteeth is found in the fact that when transmitting power or doing workthe gears are locked against intermeshing movement. Only when the clutchis operating in the open position is there an intermeshing movement, andfor many uses, as in automobiles, that will be for only a small per centof the total time Referring to Fig. 6, when the driving casing isrotating at a uniform speed with the primary gear P held stationary, thesecondary gear in its planetary movement has the revolution on its ownaxis retarded as a tooth enters an interdental space of the primary andaccelerated as it comes out. In this operation only the 12 inertia ofthe secondary gear has to be overcome, and as its mass is very smallrelative to'that of the balance. of the machinery,

both ways'from the clutch, the only effect chanical wear between theteeth under load conditions and insures a uniform distribution of thatwear.

In order that the mechanical engineer may prepare the necessary shopdrawings and give dimensions for this type of. gear, the followingtheoretical discussion is given and illustrated by diagrams, Figs. 11 to14. In the construction and in this discussion I have considered acombination having only six teeth in the smaller secondary gear.

- It will be noted, however, thatthe discustion would be the same inprinciple if the secondary had any other numbers of teeth. Fig. 11 isadiagram of an eight tooth primary and a six tooth secondary gear. Thecenters of the teeth in each gear are connected together and to thecenter of the gear by lines forming a polygon made of a number of.isosceles triangles. Itcan be demonstrated that two gears so constructedwith six and eight teeth may be set to atheoretical minimum distancecenter to center such that half the base of a triangle of one gear willcoincide with half the base of a triangle of the other gear when rotatedto the position shown in Fig. 11. The method for computing the actualdistance center to center will be demonstrated and derived from thistheoretical mt-ting.

Fig. 12 shows the gears of Fig. 11, in the same relative position butwith their centers moved further apart in a direction perpendicular tothe line that was common to both polygons. The object ofthisillustration is to show the small amount of loosening in the fitthat would attend a very perceptible increase in the gear centerdistance. Stated in trigonometrical terms, the amount of-the opening ateach of the two lines of contact on opposite sides of any tooth is gearsof one hundredth (.01) part of the tooth diameter. Fig. 14, drawn to alarger scale, is given to illustrate graphically the abovetrigonometrical statement.

If the mechanical engineer has already determined the maximum oflooseness be tween adjacent teeth which can be allowed without awasteful leakage of a moderately viscous liquid, he maynow use the aboveformula in determining the leeway ,he has in the accurate setting of thegear centers.

I take advantage of this possible leeway in the setting of the gears tomeet 'theo retical conditlons where the number of teeth in the secondarymay beheld at six and the number in the primary increased to more thaneight. From atheoretical point of view, when the number in the primaryis more than eight the polygons have to be separated, as shown inFig.12, a very small amount in order that the teeth shall clear eachother in the planetary movement of one about the other. The separation,however, is so small that when as much as three or four thousandths(.003 to .004) part of the tooth diameter is allowed for looseness inthe journal bearing fit between the teeth the necessity fordepartingfrom the setting, shown in Fig. 11, may be ignored. To illustrate by anexact statement, the theoretical separation, as illustrated in Fig. 12,necessary for ten teeth in the primary amounts to the decimal .00126part of the tooth diameter, and its effect in loosening the teeth fromthe positioniof Fig. 11 is too small to be figured with a table of sevenplace logarithms. Diagram Fig. 11 may be used therefore by the mechanicin determining the gear centers when constructing the clutch asillustrated.

The mathematics involved in the relation of the 'teeth is given inconnection With diagram, Fig. 13. Two teeth of a primary gear have theircenters M and N connected by a line. A. sequence of points P P etc.,located on the extension of a line T 1? drawn perpendicular to thecenter of the line MN represent the centers of primary gears having thenumber of teeth indicated by the sub-figure. The triangle of the pointsP MN would he, therefore, an isosceles triangle in the polygon of theprimary gear with eight teeth. Thetriangle Q wouldremain on 'the line TPuntil the tative movement of the triangle SRQ was governed by the centerof tooth B being held at a constant distance, RM, from the center oftooth M while the center Q moves" along the. line TP. Under .thatassumption the triangle-would take the position S'RQ, the center Shaving followed the curve SS. This curve can be figuredtrigonometrically and is found to be, for all practicable purposes, anarc of a circle with its center located on the line MN. The true curveis slightly fiat near the central portion of the length SS an amountapproximately one thousandth (.O01) part of a tooth diameter, and aswillbe recognized later the error in assuming it to be a circle is on theside of clearance and may be ignored.

The engineer will now appreciate that the arc of true movement ST mustnot encroach on the assumed are; SS but may be tangent to it.

P is the required distance betweenthe gear centers. calculus that whenthe two arcs are tangent at the point S the radius of the arc ST willcenter at a point P just beyond the center P of the eight toothedprimarywhen the assumed. arc SS is that of a six toothsecondar For centers at PP or P the are S will'therefore clear curve SS, and the setting shown onFig. 11 is theoretically correct. The center for the arc SS isnecessarily on the line SP, since the arcs are tangent at S. and isfound'within finite practical limits to be located at the point 7 wherethe line SP crosses the base line MN. The solution by the differentialcalculus also discloses that the radial line always intersects the lineMN at the same point V, irrespective of the number of teeth in thesecondary'gear. With more than. six teeth the center S and the asumedarc SS would be located farther to the left of the base line MN whilethe center P for the'actual curve tangent at S would be farther toright. I

Consider next that the arc ST for the six tooth secondary is actually.tangent to the curve SS at a point S for a primary gear having twentyteeth, and draw the line S P connecting S with the center P This linenecessarily passes through the center of the arc SS located, as statedabove, at oint V. Its length is equal to the radius V or SV of the arcSS plus the distance VP The distance between the point of. tangency ofthe two curves and the center It can be shown by the differential bottomof the space.

. and are su both of which can be computed from the dimensions of thegears and the location of the point V. If in this computation the Thisamount is the separation of the polygons required and as shown in Fig.12 I when the ratio of the teeth is greater than eight to six with sixin the secondary, or greater than the ratio of .5857861 to 4142139 forany other number in the secondary.

The exact location of the tangent point S" on the actual curve SS andthe absolute distance SP for any primary (the smaller of the two gearsbeing considered as the secondary) may be determined by means of trialsolutions of along trigonometrical equation; but as that refinement isof theoretical rather than practical importance the statement of theequation and its exgalanation will not be given.

Re erring to diagram, Fig. 13, at the time tooth Q moves inward on theline TP it will have a journal tight fit between short par-' allel facesin the interdental space between primary teeth M and N. During thismovement tooth Q, will act like a piston and provision must be made forthe discharge of any liquid that may be confined in the In my presentinvention I have provided for this clearance by extendin .the gearrecess spaces 2 and 2 a short gistance into the body of the main casingback of the interior faces of the gears. The extension of these recessesis shown in the transverse section of Fig. 8, which is taken on the line8-8 of Fig. 7, a little back of the primary gear. The extensions arealso shown from the opposite direction, partly in dotted outline, inFigs. 15 and 16.

The conformation of the extensions, which I will call ports, are marked31 and 31, c that an interdental space is always open to one or theother except for a fraction of movement as the center of the spacepasses the medial line of the gears nect with a port. It will thus benoted that the adjacent edges of the ports 31 and 31 are so located thatliquid cannot leak from one to the other as a space and tooth pass themedial line of the gears, but these edges are sufliciently close to themedial line to provide clearance for the liquid in each of theinterdental spaces as a tooth of the companion gear moves into it inpiston-like fashion.

Referring to Fig. 11, only that portion of the tooth surfaces subtendedbetween the base of one isosceles triangle and the line of the base ofthe adjoining triangle extended need to be cylindrical. In theillustrations of the clutch I have shown the bottoms of the spaces belowthe short parallel faces to be circular in outline to conform to teethwith full cylindrical ends. The ends of the teeth are truncated.however, somewhat outside the limit of the external angles of thepolygon as indicated b r a dotted line 32 in Fig. 11, to conform to t eperipheral wall of the gear recess and insure a liquid tight fit of thegear therein. There is, therefore, a portion of the bottom of theinterdental space that need not beemptied during the intermeshingmovement, and this surplus portion facilitates the How of the liquid upto the limit when the space is cut off from either port. When the clutchis running in the open position and during'the initial stage when theclutch is being closed centrifugal force Will more or less clear thesespaces before the intermesh takes place.

The use of the special spur gears, each with cylindrical shaped teeththat have a rolling slidin double contact between parallel faces ininterdental spaces of the companion gear, in a powertransmission devicein which the transmission is attained through the interlock of the gearsby means of a llquid medium, and in which the intermeshing movement ofthe gears when so transmitting power is relatively small and slow ascompared with the total rotative movement of the device is a subject ofU. 9.

.Letters Patent No. 1,420,798 issued to me June 27, 1922, and is notclaimed broadly, herein.

What I claim as new in my present invention and desire to secure byLetters Pat ent is:

I claim:

1. A hydraulic clutch comprisin a rotating driving casing; a drivensha't t concentrio with the casing; a pair of intermeshing spur gearpump gears carried in a. closev fitting recess in the casing. one ofsaid gears being attached to said shaft, said casing having a storagechamber and passages between the storage chamber and said gear recess,means for controlling said passages to open and close the'clutch, aliquid medium partly filling the storage chamber adapted by anintermeshing movement of the said gears to have a circulatory fiow intoor from said recess, and structural means whereby the. liquld medium mayflow lntoing driving casing, a driven shaft concentric therewith, a pairof intermeshing spur gear pump gears carried in a close fitting recessin the casin one of said gears being attached to sait shaft, said casinghaving a storage chamber and passages between the storage chamber andsaid gear recess, valve means for controlling said passages to open andclose the clutch, a liquid medium partly filling the storage chamberadapted by an intermeshing movement of the said gears to-have acirculatory flow into or from said recess, and structural means wherebysaid liquid medium may flow into but not from said recess with theclutch closed and flow from but not into said recess, with the clutchopen; said structural means being symmetrical and operative with theclutch rotating in either direction.

3. A hydraulic clutch comprising a rotating driving casing, a drivenshaft concentric therewith, a pair of intermeshing spur gear pump gearscarried in a close fitting recess in the casing, one of said gears beingattached to said shaft, said casing having a storage chamber andpassages between the storage chamber and said gear recess, valve meansfor controlling said passages, and a liquid medium confined in andfilling said recess when the controlling valve means is in one positionand cleared and excluded from said recess when the valve means is inanother position.

4. A hydraulic clutch comprising a rotating driving casing, a drivenshaft concentric therewith, a pair of intermeshing spur gear pump gearscarried in a close fitting recess in the casing, one of said gears beingattached to said shaft. said casing having a storage chamber andpassages between the storage chamber and the said gear recess,v

valve means for controlling said passages, and a liquid medium confinedin and filling said recess when the controlling valve means is in oneposition and c eared and excluded from said recess when the valve meansis in another position, the construction being symmetrical and' operablewith the driving casingrotating in either direction.

5. In a hydraulic clutch of the spur gear pump type wherein, of the pumpelements, the pump casing is rotatable to carry the secondary gear in aplanetary movement about the primary gear and constitutes the drivingmember, and the shaft attached to the primary gear concentric with thecasing constitutes the driven member, and wherein and driven membersestablishes a suction and discharge action with the elements acting as apump, the combination of said pum elements: said casing having a storagechamber and two series of passages, a liquid medium in said storagechamber held away from the center of rotation by centrifugal action, andtwo valves cooperating respec tively with said two series of passages tocontrol the suction and discharge action of said pump elements on saidliquid medium and adapted in one position to close the discharge side ofthe pump and connect the suction side to the storage chamber at a pointsubmerged by the liquid medium, and, in another position, to connectboth discharge and suction sides to the storage chamber at points notsubmerged by the liquid medium.

6. A hydraulic clutch of the spur gear pump type comprising a rotatingcasing for the main driving member, a shaft concentrio with the casingfor the driven member, a pair of intermeshing spur gears set in a liquidtight fit in a gear recess in the casing, one of said gears beingattached to the shaft, said casing having a storage chamber and 'twoseries of passages between said chamber and the gear recess and arrangedon opposite sides of said recess, a liquid medium in the storage chamberadapted to be held to the radially outer portions of said chamber by thecentrifugal force generated by the rotating casing, and two operablevalves for governing the flow of the liquid through the passages to "andfrom the gear recess and adapted in one position, to confine a portionof the liquid medium in the gear recess and prevent intermeshingmovement of the gears, and, in another position, to permit the clearanceof the liquid medium from the gear recess and the free intermeshing.movement of the gears.

7. A hydraulic clutch of the spur gear pump type adapted to be equallyeffective under a reversal of strain between the interlocked parts whenin the-closed position or under a reversal of relative movement of theunlocked parts when in the open position, and comp-rising a rotatingcasing for the main driving member, a shaft concentric with the casingfor the driven member; a

pair of intermeshing spur gears' set in a liquid tight fit'in a gearrecess in the casing, one of said gears being attached to the shaft,said casing having a storage. chamber and two series of passages betweensaid chamber and the gear recess and arranged on opposite sides of saidrecess, a liquid me dium in the storage chamber adapted to be held tothe radiallyvouter portions of said chamber by the centrifugal forcegenerated by the rotating casing; two operable valves for governing theflow of the liquid through the passages to vand from the gear recess,and two automatic check valves located in said passages on oppositesides of the gear recess and adapted to open only for a flow of theliquid toward said recess.

8. In a clutch of the hydraulic pump type, a pump mechanism comprisingrotatably mounted pump elements constituting the driving and drivenclutch members, a storage chamber rotatable with the driving clutchmember, separate passages connecting the radial inner and outer portionsrespectively of said storage chamber with said pump mechanism, valvemeans interposed in each of said assagesfor controlling the flowtherethroug 1, and a fluid medium, part liquid and part gaseous in saidstorage chamber, the liquid portion, in operation, being held in theradially outer portion of the chamber by centrifugal action.

9. A hydraulic clutch of the spur gea pump type comprising a mainrotating casing A with cover plates B and C for the drlving member, ashaft F concentric with the casing for the driven member, intermeshinggears P and S set in a liquid tight fit in a gear recess in the casing,the gear P being attached'to the shaft F, said casing having a storagechamber J, and two series of passages between the storage chamber andthe opposite sides of said gear recess, two piston valves 3 and 3 forgoverning said passages and means for shifting the piston valves jointlyfrom one to the other-of two 0perative positions andnthereby eitherpermit the independent rotative movements of the driving and drivenmembers or effect the interlocking thereofby a liquid medium confined inthe gear'recess.

10. In a clutch of the hydraulic pump type wherein a rotating casingcontaining the pump elements, the liquid medium and the operatingvalves, constitutes the driving member, and a shaft concentric with thecasing and attached toone of the pump elements constitutes the drivenmember; the combination of said rotating casing, pump elements, liquidmedium and valves, said casing having a. storage chamber and a passagefrom a radially outer portion of the storage chamber adapted to beopened to the suction side of said pump elements when the operatingvalves are in the closed clutch position, and said casing having twopassages from a radially inner portion of the storage chamber adapted toopen respectively one to the suction side and one to the discharge sideof the pump elements when the operating valves are in the open clutchposit-ion.

11. In a clutch of the hydraulic pump type wherein a rotating casing,containing the pump elements, the liquid medium and constitutes thedriven member; the combination in and with said rotating casing and thesaid parts contained therein, said casing having a storage chamber andtwo passages leading from radially outer portions of the storagechamber, one to the suction side and one to the discharge side ofsaidpump elements, automatic check valves normally closing said passagesand one or the other of which is opened by suction action of the pumpelements when said operating valves are in closed clutch position, andtwo other passages leading from a radially inner portion of the storagechamber and adapted to be opened respectively one to the suction sideand one to the discharge side of the pump elements when said operatingvalves are in the open clutch position the arrange mentpermitting theoperation of the clutch for a rotation of the driving member in eitherdirection.

12. A hydraulic clutch comprising a rotating casing, a shaft concentricwith the axis of rotation of said casing, a pump mechanism actuated byany relative rotary movement of said casing and said shaft, said casinghaving a storage chamber and separate passages connecting said storagechamber and said pump mecha-nlsmand constitutlng suction and dischargepassages for the latter,

a fluid medium separated into liquid and gas portions in said storagechamber and said passages, and controlling valve means interposed ineach of said passages for opening and closing the clutch, said valvemeans cooperating with said passages to cut off the discharge of fluidmedium from said pump mechanism and limit the suction thereof to liquidwhen the clutch is closed, and permit the discharge of fluid medium fromsaid pump mechanism and limit the suction thereof substantially-to gaswhen the clutch is open.

13. A hydraulic clutch comprising a rotat ing casing having a number ofrecesses and passages, a shaft concentric with said casinga fluidmedium, part liquid and part gaseous, filling said recesses andpassages, a pump mechanism actuated by any relative rotary movement ofsaid casing and shaft to cause a flow of the fluid medium through therecesses and passages, and valve means for controlling said passagesadapted to cut off the discharge of fluid medium from said pumpmechanism and limit the suction action thereof to liquid when the clutchis closed, and permit the discharge of fluid medium from said pumpmechanism and limit the suction action thereof substantially to gas whenthe clutch is open, the said casing having a contracted duct foradmitting a small amount of the liquid to the suction side of the pumpmechanism for lubrication when the clutch is open.

14. A hydraulic clutch of the spur gear pump type, wherein for theclosed clutchposition the spur gears are interlocked by means of aliquid medium confined within the gear recess, and wherein for the openclutch position the spur gears have a free intermeshing movement, andcomprising a rotating casing for the driving member; a shaft concentricwith the casing for the driven member, said casing having a series ofrecesses and passages, a fluid medium, part liquid and part gaseous,filling said recesses and passages, a pair of inter-meshing spur gearpump gears set within one of, said recesses, one gear being attached tothe said shaft, and the other being rotatably mounted in the recess, andadapted by their intermeshing movement to produce a circulatory flow ofthe fluid medium through said recesses and passages, the spur gearshaving teeth each with cylindrically shaped bearing surfaces on oppositesides adapted to have a rolling sliding fit between short parallelsurfaces in the interdental space of the companion gear, and a pair ofoperable valves for governing the flow of said fluidmedium through therecesses and passages and thereby, in open clutch position, maintainingthe gear recess substantially empty of the liquid 'portion of the fluidmedium.

age chamber with said pump mechanism and constituting the suction anddischarge passages respectively for the latter, a valve for opening andclosing said discharge passage to open and close the clutch and a valveco operating with said suction passage to limit the suction action ofthe pump to the liquid portion of the medium when the clutch is closedand substantially to the gaseous portion thereof when the clutch isopen,

16. In a clutch of the hydraulic pump type, the combination of a pumpmechanism wherein the pump casing is rotatable and constitutes thedriving member and wherein the pump shaft extending into the pump casingconcentric therewith constitutes the one of said passages andcooperating there with to admit only liquid to the suction side of thepump mechanism in closed clutch po-- sition and only gas in open clutchposition and another valve interposed in the other the supply of liquidand gas respectively to the suction side thereof, and controlling valvemeans interposed in each of said passages and arranged, in closed clutchposition to close the discharge and gas supply passages and-permit flowthrough the liquid supply passage and, in open clutch position, to closethe liquid supply passage and permit flow through'the discharge and gassupply passages.

18. In a clutch of the hydraulic pump type, a pump mechanism comprisinga r0- tary casing having a pump chamber, a storage chamber and separatepassages connect ing said storage chamber to the suction and dischargeports of said pump chamber. a concentrically mounted shaft extendinginto said casing, a pump element in said pump chamber operativelyconnected to said shaft. a fluid medium, separated into liquid and gasportions, in said storage chamber, and valve means interposed in' eachof the passages between said pump and storage chambers and adapted. inone position, to close the discharge from said pump chamber and connectthe suction port thereof to the liquid containing portion only of thestorage chamber and, in another position, to open the discharge from thepump chamber and connect the suction port thereof to the gas containingportion only of the storage chamber.

19. In a clutch of the hydraulic pump D type, a pump mechanismcomprising a ro' tary casing having a pump chamber, a stor-. age chamberand separate passages connecting said storage chamber to the suction anddischarge ports of said pump chamber, a concentrically mounted shaftextending into said casing, a pump element in said pump chamberoperatively connected to said shaft, a fluid medium, separated intoliquid and gas portions, in said storage chamber, and valve meansinterposed in each ofthe pas sages between said pump and storage charm-'hers and adapted, in one position, to close the discharge from said pumpchamber and con-. nect .the suction port thereof to the liquidcontaining portion only of the storage chamber and, in another position,to open the discharge from the pump chamber and connect the suction portthereof to the gas containing portion only of the storage chamber, saidvalve means having an intermediate position for partly closing thedischarge from said pump chamber and for connecting the suction portthereof both to the liquid and gas containing portions of the storagechamber.

20. In a clutch of the hydraulic pump type, a rotatable casingcomprising a main section recessed in its opposite end faces to formrespectively a gear pump chamber and a storage chamber and havingseparate suction and discharge passages connecting said chambers. coverplates secured in liquidtight fashion to the ends of said main sectionand forming the outer walls of said chambers, a shaft extending throughthe storage chamber and the adjacent cover plate and into said pumpchamber, intermeshing spur pump gears in said pump chamber, one of saidgears being connected to said shaft, a piston. valve for opening andclosing said discharge passage, said main casing section having achamber for said piston valve, the

opposite ends of said piston chamber being in communication with saidstorage chamber, one such communication being restricted to retard theclosing movement of said valve and means extending into said storagechamber through the adjacent cover plate for shifting said valve.

21. In a clutch of the hydraulic pump type, a rotatable casingcomprising a main section recessed inits opposite end faces to form agear pump chamber and a storage chamber respectively sages connectingsaid chamber to the suction and discharge sides .of said pump chamber,cover plates secured tothe ends of said main section and forming theouter walls of said chambers, a. shaft extending through the storagechamber and the adjacent cover plate and into said pump chamber. spurpump gears in the latter chamber, one being connected to said shaft,controlling valve mechanism co-operating and having paswvithsaidpassages and arranged, in closed clutch position, to connect only thesuction side of the pump chamber and the radially outer portion of thestorage chamber and, in open clutch position, to connect both thesuction and discharge sides of the pump chamber to the radially centralportion only of the storage'chamber, and shifter means for the valvemechanism extending into the storage chamber through the adjacent coverplate.

WILLIAM S. WES-TON.

